I have used a chainsaw for about 25 years and I have always used a round file on the teeth. I have never filed down the "drags" or whatever the correct term is. I do have a cheater on the file though. I got it at Wal-Mart. It attaches to the file, and it shows the correct angle you should file. Every time I file it, it cuts like a brand new chain. Unless I get it in the dirt, then it is time to file again. Worst thing in the world for a chainsaw is dirt!
Wise words & Great link..Even if you're just cutting a few pieces of wood each day you definitely need to sharpen your saw by now! It takes some practice, but not too hard to learn - at least for "touch-up" sharpening.
Checkout Chain Saw Sharpeners Guide website for some good information about sharpening your chainsaw. It's not the prettiest site, but it will help you learn the basics.